Because you follow wherever the evidence leads you.
The slope of the line
is
.
The line perpendicular to the above line has slope
Its equation is
. Since this line passes through,
,

Thus the equation of the line in slope intercept form is 
2d+1=3d+5.
If both equations equal c, then both equations can be equal to each other.
Answer:
1.5 for each song.
Step-by-step explanation:
subtract $6.99 by $21.99 = 15 divided by 10 = 1.5